Loss of surface skid resistance

Loss of surface skid resistance is a skid hazard associated with smooth and slippery surface, which directly affects traffic safety. Unlike all other surface distresses, a smooth and slippery surface does not affect the structural deterioration of the pavement. 

Slippery surface may result from polishing and abrasion of the surface aggregate or asphalt bleeding. Both factors reduce the macro- and micro-texture of the pavement surface and the surface skid resistance provided. 

In the presence of water, the surface becomes more slippery hence, the pavement s surface becomes more dangerous. An excess amount of water may result in aquaplaning, a situation where skid resistance is eliminated. 

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The cause for loss of surface skid resistance is exclusively the wear of the surface texture provided, the polishing of the fine aggregate and the polishing of the exposed coarse... 

Bleeding or flushing of the binder results in a surface that is too rich in binder. Bleeding can cause hazardous conditions owing to loss of surface skid resistance. 

Inadequate curing before opening the pavement to traffic may result in concrete with poor skid resistance owing to loss of surface mortar. Areas with heavy traffic or lanes for commercial vehicles are going to suffer first. 

The PTV is defined as the loss of energy as the standard rubber-coated slider assembly slides across the test surface and provides a standardised value of slip/skid resistance (CEN EN 13036-4 2011). 

The situation is complicated, however, because some of the drag on a skidding tire is due to the elastic hysteresis effect discussed in Section XII-2E. That is, asperities in the road surface produce a traveling depression in the tire with energy loss due to imperfect elasticity of the tire material. In fact, tires made of high-elastic hysteresis material will tend to show superior skid resistance and coefficient of friction. 

All types of surface distresses occurring in flexible pavements can be classified into four categories cracking, distortion, disintegration and loss of skid resistance. 

In furnaces with bottom zones, such as pusher or walking beam steel reheat furnaces, each skid rail, on which the loads rest or slide, consists of a schedule 160 pipe, 6.625" (0.1683 m) OD with 0.718" (18.24 mm) wall thickness, through which cooling water is circulated. A solid skid wear bar is securely welded onto the top surface of the pipe. The skid wear bars are often small diameter bars of heat-resisting, wear-resisting material. Their small diameter allows less contact area with the load pieces, thereby minimizing heat loss from the loads. 

The use of ultrafine silica as a reinforcement for the treads of tyres has come into prominence in recent years because, as well as offering better resistance to wet skidding than does carbon black reinforcement, it also gives better low-loss properties to the tread compound, with consequent improvement in resistance to rolling and therefore a reduction in fuel consumption. Silica resembles carbon black in its particle morphology, but the surface properties are very different (see Chapter 19). 

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